It appears we may have a cold AND wet winter, so I am planning ahead by buying something that will melt ice on my sidewalks. Will ice melt products harm my plants and lawn? Randy W., Broken Arrow
Products used to melt ice on walks and driveways may harm plants, but this depends on what and how much is used. Most of the chemicals marketed today to melt ice are actually just salts that lower the freezing point of water. All are useful if the labeled directions are followed carefully.
Four of the most commonly used chemicals are sodium chloride (table salt), calcium chloride, calcium magnesium acetate and urea. All are types of salts, except urea, which is a chemical normally found in fertilizers.
These products thaw ice but also have some undesirable effects. They may cause corrosion of concrete and metal, water pollution, as well as harm to plants.
Sodium chloride is the cheapest and most widely used for ice melt. But, it has a significant potential for corrosion and plant damage in high concentrations. Calcium chloride and urea have similar risk for corrosion, but are less harmful to plants. Calcium magnesium acetate does not corrode or pollute water and does not harm plants. However, as you may have already guessed, it also is the most expensive.
Damage to plants occurs in two ways. First, when directly when splashed on plants; secondarily, when absorbed into the soil. When slush-containing salt comes in contact with a plant, it may cause direct injury to evergreen leaves and buds as well as stems of deciduous plants. This injury, especially in deciduous plants, could go unsuspected as the damage may not appear until next spring.
Salts that filter into the soil can kill plant roots by dehydrating them. It can also raise the soil pH to undesirable levels, thus affecting the overall health of the plant and its ability to take up proper nutrients. This is the same as fertilizer "burn" that gardeners are familiar with when too much fertilizer is put (or spilled) in one location. In addition, large amounts of sodium from sodium chloride can damage the soil structure, making it less friendly to plants.
So, what do you do? The ideal approach to ice and snow is to remove as much as possible by hand. Not exactly what you wanted to hear, right? Then, if you feel it is needed, apply an ice melt chemical to help remove the last layer. Avoid the "more is better" mindset and always follow label directions. Mixing sand in a 3-to-1 ratio with ice melt can reduce the need for chemicals and provides added traction to feet and tires.
Harmful effects of these chemicals may be minimized by hosing salt off plants, when it is possible. Much of the salt in soils may be removed if irrigated with generous amounts of water. We are fortunate that ice and snows are not long-term winter problems in our area, and that most people are able to cope without ice melt chemicals.